Reliable Control via Additive Redundant Adaptive Controller

A multiple controller structure, consisting of a typical feedback controller and an additive redundant adaptive controller, is proposed as a means of enhancing reliability of the control system. The control system ensures the performance of tracking a given set-point input under failure in one of controllers or under parameter change of the plant. In case that the main controller is a set-point tracking controller with static gains and the redundant controller is a parallel MRAC whose reference model is the closed-loop combination of the plant and the main controller, it is proved that the tracking error between the command input and the plant output converges to zero against various failure modes, and further that reliability measured by MTTF(Mean Time To Failure) is greater than that of the system with only a single main controller. A simulation example is provided to illustrate reliable operation of the proposed control system.